Inverse of 2 x 2 Matrix

Inverses of Matrices - How it Works - Video

Inverse Indenties

Inverse Identities:

For matrix to have an identity, the matrix must be a square. For example, it must be 2 x 2, 3 x 3, 4 x 4, 5 x 5, and so on.

Each identity is the diagonal from top left to bottom right contains ones and the rest are zeros.

Like in multiplication where if we multiply by the multiplicative identity the answer will be 1. For example 5 * (1/5) is 1. When we multiply, a matrix and it's inverse matrix the resultant matrices will just have the number 1 inside.

Example 1 - Step 1

Example 1 - Step 1:

Here we have added the identity matrix to make an augmented matrix.

We replaced R₂ with 4 * R₁ - * R₂ and the reason is that we want the element a_2,1 or 4 in this case to be 0.

So we multiplied the first row by 4 to that so our new R₁ is 4, 8, 4, 0. Then we subtract our new R₁ and R₂ to get 0, 2, 4, -1.

We need our principle diagonal (top left to bottom right) to be only 1s and our secondary diagonal (bottom left to top right) to be 0s.

Example 1 - Step 2

Example 1 - Step 2:

We replaced R₁ with R₁ - * R₂ and the reason is that we want the element a_1,2 or 2 in this case to be 0.

So we subtract our R₁ and R₂ to get 1, 0, -3, 1.

Example 1 - Step 3

Example 1 - Step 3:

We replaced R₂ with (1/2) * R₂ and the reason is that we want the element a_2,2 or 2 in this case to be 1.

So we multiply each element in R₂ by (1/2) to get 0, 1, 2, -1/2.

Example 1 - Answer

Example 1 - Answer:

Now the numbers are after vertical line is the inverse of original matrix. So in R₁ we have -3 and 1, and in R₂ we have 2 and (-1/2).

Live Worksheet

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